Recently, an eco-friendly electric vehicle which may have reduced energy consumption and environmental pollution has been variously developed, such as, an eco-friendly electric vehicle which includes a fuel cell vehicle and a hybrid vehicle. The fuel cell vehicle is a vehicle that uses electricity generated by an electrochemical reaction of hydrogen and oxygen as an energy source. The hybrid vehicle is a vehicle that uses an internal combustion engine while driven at a high speed or driven on an uphill road and uses electricity as the energy source while it is driven at a low speed or stopped.
Generally, the existing internal combustion engine vehicle is driven by driving power which is generated by an explosive reaction of fossil fuel with oxygen in the air within an engine to convert the chemical energy into mechanical energy, while the fuel cell vehicle is driven by electric energy which is generated by an electrochemical reaction of hydrogen supplied through a high pressure hydrogen tank or a reformer with oxygen in the air supplied through an air turbo compressor within a fuel cell stack. In other words, the fuel cell system is an apparatus that directly converts energy of fuel into electrical energy and is a system which includes a pair of electrodes configured of an anode and a cathode, having an electrolyte disposed therebetween and obtains electricity and heat by an electrochemical reaction of ionized fuel gas.
A polymer electrolyte membrane fuel cell may have a high current density, a low operation temperature, low corrosion, and a reduced loss of electrolyte, and as a result, has started to be developed as a power source for military use or a space ship. Recently, however, the polymer electrolyte membrane fuel cell may have a high output density and may be modularized due to a simplified apparatus, and as a result, research for applying the polymer electrolyte membrane fuel cell as a power source for a vehicle has been actively conducted.
The fuel cell system includes a fuel cell stack configured to generate electric energy from an electrochemical reaction of reaction gas, a hydrogen supply apparatus configured to supply hydrogen which is fuel to the fuel cell stack, an air supply apparatus which supplies air including oxygen which is an oxidizing agent required for the electrochemical reaction to the fuel cell stack, and a heat and water management system configured to emit heat which is a byproduct from the electrochemical reaction of the fuel cell stack to the exterior to optimally adjust an operation temperature of the fuel cell stack and perform a water management function.
In this configuration, the heat and water management system includes an ion filter, in which the ion filer removes metal ions from cooling water which circulates the fuel cell stack and then is discharged to increase a lifespan of the fuel cell and stabilize the fuel cell system. In other words, the ion filter of the fuel cell vehicle is disposed on a stack cooling water loop to perform ion filtering to prevent an electric shock due to a high output stack that corresponds to 100 kW, thereby assuring electric stability of the system.
For example, an ion resin is installed within a cartridge to remove and manage electric conductivity increased in proportion to an increase in the amount of cation/anion present in the stack cooling water so that the electric conductivity is equal to or less than a predetermined level, thereby increasing insulation stability of the vehicle. Therefore, an inside of the ion filter includes the ion resin which substantially filter ions contained in the cooling water and the cooling water which circulates the fuel cell stack and is discharged enters the ion filter to have the metal ions removed therefrom by the ion resin in the ion filter and then again circulates the fuel cell stack, thereby appropriately adjusting ionicity, that is, electric conductivity within the stack cooling water
Meanwhile, the electric conductivity of the stack cooling water is measured by an electric conductivity sensor. In particular, when the electric conductivity measured by the electric conductivity sensor is equal to or greater than a reference value, the ion filter cartridge is replaced to manage the electric conductivity in the stack cooling water to be equal to or less than the predetermined level. For example, the electric conductivity is measured by the electric conductivity sensor and a cooling water electric conductivity signal is periodically transferred to an fuel cell control unit (FCU) through controller area network (CAN) communication to determine whether to replace the ion filter cartridge.
However, in the case of the foregoing electric conductivity sensor sensitive method, a volume of the electric conductivity sensor is increased and costs (100,000 per one) thereof are increased, and thus the electric conductivity sensor sensitive method is disadvantageous in a layout aspect and an economical aspect. Further, when the electric conductivity sensor and the CAN communication are poor, it may be difficult for a consumer to determine the replacement timing of the ion filter cartridge.